Selenocarboxylates alkylation

As well as acylation of selenols, alkylation of selenocarboxylates with alkyl halides is one of the most straightforward methods for synthesis of selenol esters. However, known examples of selenol esters synthesized using this strategy have been limited to a few cases, due to the difficulty of the preparation of selenocarboxylates. 

Piperidinium selenocarboxylates (15 equation 10) have been isolated in high yields from the reaction between diacyl diselenides and piperidine. The salts (15) dissolved in common protic and aprotic solvents and readily reacted with alkylating agents such as phenacyl bromide to give the corresponding esters in almost quantitative yields. ... 

In 1994, successful isolations of various alkyl and aryl selenocarboxylic acids [14] enabled them to undergo exact reactions. Reactions of selenocarboxylic acids with dicyclohexylcarbodiimide (DCC) yield the corresponding diacyl selenides 25 and selenourea 26 quantitatively (Scheme 15) [14], as in reactions of thio- [44] and dithiocarboxylic acids [45,46]. In air,selenocarboxylic acids are immediately oxidized to afford the corresponding diacyl diselenides [13, 14]. Also, thio- and dithio-carboxylic acids readily react with aryl isocyanates to give acyl carbamoyl [47,48] and thioacyl carbamoyl sulfides [49, 50], respectively. 

Carbonyl sulfide (SCO) reacts with Grignard reagents at the carbonyl carbon [87], and this has been used to introduce a thiocarboxyl unit into organic molecules. For example, thiocarboxylations of enolates [88], phosphorous ylides [89], and an acyllithium [90] have been reported. Selenocarboxylation to organocopper reagents with carbonyl selenide (SeCO), followed by alkylation, gave selenol esters (Eq. 42) [91]. 

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